text: /*
   * Copyright (c) 2012 Clément Bœsch
   *
   * This file is part of FFmpeg.
   *
   * FFmpeg is free software; you can redistribute it and/or
   * modify it under the terms of the GNU Lesser General Public
   * License as published by the Free Software Foundation; either
   * version 2.1 of the License, or (at your option) any later version.
   *
   * FFmpeg is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   * Lesser General Public License for more details.
   *
   * You should have received a copy of the GNU Lesser General Public
   * License along with FFmpeg; if not, write to the Free Software
   * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
   */
  
  #ifndef AVFORMAT_SUBTITLES_H
  #define AVFORMAT_SUBTITLES_H
  
  #include <stdint.h>
  #include <stddef.h>
  #include "avformat.h"
  #include "libavutil/bprint.h"
  
  enum sub_sort {
      SUB_SORT_TS_POS = 0,    ///< sort by timestamps, then position
      SUB_SORT_POS_TS,        ///< sort by position, then timestamps
  };
  
  enum ff_utf_type {
      FF_UTF_8,       // or other 8 bit encodings
      FF_UTF16LE,
      FF_UTF16BE,
  };
  
  typedef struct {
      int type;
      AVIOContext *pb;
      unsigned char buf[8];
      int buf_pos, buf_len;
      AVIOContext buf_pb;
  } FFTextReader;
  
  /**
   * Initialize the FFTextReader from the given AVIOContext. This function will
   * read some bytes from pb, and test for UTF-8 or UTF-16 BOMs. Further accesses
   * to FFTextReader will read more data from pb.
   * If s is not NULL, the user will be warned if a UTF-16 conversion takes place.
   *
   * The purpose of FFTextReader is to transparently convert read data to UTF-8
   * if the stream had a UTF-16 BOM.
   *
   * @param s Pointer to provide av_log context
   * @param r object which will be initialized
   * @param pb stream to read from (referenced as long as FFTextReader is in use)
   */
  void ff_text_init_avio(void *s, FFTextReader *r, AVIOContext *pb);
  
  /**
   * Similar to ff_text_init_avio(), but sets it up to read from a bounded buffer.
   *
   * @param r object which will be initialized
   * @param buf buffer to read from (referenced as long as FFTextReader is in use)
   * @param size size of buf
   */
  void ff_text_init_buf(FFTextReader *r, void *buf, size_t size);
  
  /**
   * Return the byte position of the next byte returned by ff_text_r8(). For
   * UTF-16 source streams, this will return the original position, but it will
   * be incorrect if a codepoint was only partially read with ff_text_r8().
   */
  int64_t ff_text_pos(FFTextReader *r);
  
  /**
   * Return the next byte. The return value is always 0 - 255. Returns 0 on EOF.
   * If the source stream is UTF-16, this reads from the stream converted to
   * UTF-8. On invalid UTF-16, 0 is returned.
   */
  int ff_text_r8(FFTextReader *r);
  
  /**
   * Return non-zero if EOF was reached.
   */
  int ff_text_eof(FFTextReader *r);
  
  /**
   * Like ff_text_r8(), but don't remove the byte from the buffer.
   */
  int ff_text_peek_r8(FFTextReader *r);
  
  /**
   * Read the given number of bytes (in UTF-8). On error or EOF, \0 bytes are
   * written.
   */
  void ff_text_read(FFTextReader *r, char *buf, size_t size);
  
  typedef struct {
      AVPacket *subs;         ///< array of subtitles packets
      int nb_subs;            ///< number of subtitles packets
      int allocated_size;     ///< allocated size for subs
      int current_sub_idx;    ///< current position for the read packet callback
      enum sub_sort sort;     ///< sort method to use when finalizing subtitles
      int keep_duplicates;    ///< set to 1 to keep duplicated subtitle events
  } FFDemuxSubtitlesQueue;
  
  /**
   * Insert a new subtitle event.
   *
   * @param event the subtitle line, may not be zero terminated
   * @param len   the length of the event (in strlen() sense, so without '\0')
   * @param merge set to 1 if the current event should be concatenated with the
   *              previous one instead of adding a new entry, 0 otherwise
   */
  AVPacket *ff_subtitles_queue_insert(FFDemuxSubtitlesQueue *q,
                                      const uint8_t *event, size_t len, int merge);
  
  /**
   * Set missing durations, sort subtitles by PTS (and then byte position), and
   * drop duplicated events.
   */
  void ff_subtitles_queue_finalize(void *log_ctx, FFDemuxSubtitlesQueue *q);
  
  /**
   * Generic read_packet() callback for subtitles demuxers using this queue
   * system.
   */
  int ff_subtitles_queue_read_packet(FFDemuxSubtitlesQueue *q, AVPacket *pkt);
  
  /**
   * Update current_sub_idx to emulate a seek. Except the first parameter, it
   * matches AVInputFormat->read_seek2 prototypes.
   */
  int ff_subtitles_queue_seek(FFDemuxSubtitlesQueue *q, AVFormatContext *s, int stream_index,
                              int64_t min_ts, int64_t ts, int64_t max_ts, int flags);
  
  /**
   * Remove and destroy all the subtitles packets.
   */
  void ff_subtitles_queue_clean(FFDemuxSubtitlesQueue *q);
  
  /**
   * SMIL helper to load next chunk ("<...>" or untagged content) in buf.
   *
   * @param c cached character, to avoid a backward seek
   */
  int ff_smil_extract_next_text_chunk(FFTextReader *tr, AVBPrint *buf, char *c);
  
  /**
   * SMIL helper to point on the value of an attribute in the given tag.
   *
   * @param s    SMIL tag ("<...>")
   * @param attr the attribute to look for
   */
  const char *ff_smil_get_attr_ptr(const char *s, const char *attr);
  
  /**
   * @brief Same as ff_subtitles_read_text_chunk(), but read from an AVIOContext.
   */
  void ff_subtitles_read_chunk(AVIOContext *pb, AVBPrint *buf);
  
  /**
   * @brief Read a subtitles chunk from FFTextReader.
   *
   * A chunk is defined by a multiline "event", ending with a second line break.
   * The trailing line breaks are trimmed. CRLF are supported.
   * Example: "foo\r\nbar\r\n\r\nnext" will print "foo\r\nbar" into buf, and pb
   * will focus on the 'n' of the "next" string.
   *
   * @param tr  I/O context
   * @param buf an initialized buf where the chunk is written
   *
   * @note buf is cleared before writing into it.
   */
  void ff_subtitles_read_text_chunk(FFTextReader *tr, AVBPrint *buf);
  
  /**
   * Get the number of characters to increment to jump to the next line, or to
   * the end of the string.
   * The function handles the following line breaks schemes:
   * LF, CRLF (MS), or standalone CR (old MacOS).
   */
  static av_always_inline int ff_subtitles_next_line(const char *ptr)
  {
      int n = strcspn(ptr, "\r\n");
      ptr += n;
      if (*ptr == '\r') {
          ptr++;
          n++;
      }
      if (*ptr == '\n')
          n++;
      return n;
  }
  
  /**
   * Read a line of text. Discards line ending characters.
   * The function handles the following line breaks schemes:
   * LF, CRLF (MS), or standalone CR (old MacOS).
   *
   * Returns the number of bytes written to buf. Always writes a terminating 0,
   * similar as with snprintf.
   *
   * @note returns a negative error code if a \0 byte is found
   */
  ptrdiff_t ff_subtitles_read_line(FFTextReader *tr, char *buf, size_t size);
  
  #endif /* AVFORMAT_SUBTITLES_H */
  